Pilot Study to Evaluate Feasibility of DensiProbe Spine Assessing Bone Strength in Spinal Surgery

• Surgeon's compliance- and handling-oriented questionnaire [ Time Frame: Baseline ] [ Designated as safety issue: No ]
  The general satisfaction of the surgeon with DensiProbe Spine as well as specific problems that are likely to occur during the measurement with DensiProbe Spine will be assessed
  
  
• Intra- and post-operative adverse events [ Time Frame: Up to 2 months postsurgery ] [ Designated as safety issue: Yes ]
  All intra- and postoperative adverse events will be assessed and analyzed regarding their relationship to the study device
  
  

• Bone mineral density [ Time Frame: Baseline ] [ Designated as safety issue: No ]
  The bone mineral density will be measured preoperatively in the lumbar spine (L1-L4) using DXA in order to assess local bone status.
  
  
• Pedicle screw migration [ Time Frame: 2 months postsurgery ] [ Designated as safety issue: No ]
  The migration of the pedicle screw will be performed by measuring the angle between the pedicle screw axis and the caudal endplate. The amount of screw migration is defined as the difference in that angle between the baseline (postoperative) and the two month lateral x-rays
  
  
• QCT analysis of bone biopsies [ Time Frame: Baseline ] [ Designated as safety issue: No ]
  For each vertebral body under investigation a probe of trabecular bone is obtained to determine bone quality using quantitative micro-CT analysis
  
  
• Application of bone cement [ Time Frame: Baseline ] [ Designated as safety issue: No ]
  For each patient the surgeon decides whether or not augmentation with bone cement is necessary
  
  

Osteoporotic fragility fractures often occur in the spine. A common surgical technique is the transpedicular fixation using pedicle screws. A major complication of this treatment is a cut-out or back-out of the screw due to insufficient anchorage of the implant in the vertebral body.

A new mechanical device was developed in order to provide the surgeon with intraoperative information about the mechanical strength of the cancellous bone. In cases of low bone quality, the treatment can be adapted to the patient's condition, for example by augmentation of the screw anchorage using bone cement. However, this treatment involves a risk of cement leakage and subsequent pulmonary embolism or nerve damage. Furthermore, cement augmentation is time-consuming. Therefore, there is a need for a diagnostic device that can intraoperatively support the surgeon's decision on the appropriate treatment.

DensiProbe Spine was developed accordingly to the clinically approved DensiProbe Hip, which was designed for the same diagnostic reasons in patients with hip fractures undergoing fracture fixation with the dynamic hip screw (DHS). However, the application of bone strength measurements in the spine is in so far different to the hip as the anatomical dimensions in the spine are much smaller and lower values of bone mineral density (BMD) and bone strength are expected.

The objective of this pilot study is to investigate the handling and feasibility of the newly developed DensiProbe Spine measurement device. In case of a positive result of the pilot study, a multicenter cohort study will be performed in order to clinically validate the DensiProbe Spine device by assessing the correlation between DensiProbe Spine measurements and the amounts of pedicle screw migration in patients undergoing transpedicular fixation.